Underwater noise pollution
The ocean is a noisy place. Just like an ocean swell, sound waves travel very far underwater. In fact, sound can travel five times faster and further through water than air, and sunlight does not penetrate very deeply so many marine species use sound instead of vision as their primary sense.
Whales and dolphins have expertly adapted to life under the waves – they produce a huge variety of different sounds and break a few records in the process.
Blue and fin whales are the two largest creatures ever to have lived on Earth. They use low frequency sounds that can only be felt as vibrations by humans, but can be heard thousands of kilometres away by other whales.
Male humpback whales sing the longest, most complex songs of any species. They can sing for hours, but no one knows for sure the purpose of their beautiful songs. Dolphins and toothed whales use high frequency sounds for echolocation that allows them to get information about their surroundings and find their prey. Sperm whales produce the loudest sounds of any species to locate squid in the depths.
A few centuries ago, the sounds in the ocean came only from the marine life that lived there as well as a variety of natural ambient sounds, such as rain, cracking sea ice, breaking waves, and undersea earthquakes. But our modern world with its trade, travel and globalisation has changed this. Today, human activities create a huge cacophony of underwater noise, to the extent that ocean background noise is now dominated by the sounds created by long-distance shipping. The noise from ship traffic has doubled every decade since the 1960s creating noise pollution that has the potential to mask important messages that whales, dolphins and other marine species need to communicate with each other. This underwater racket disrupts essential daily activities such as feeding and breeding patterns, as well as causing individuals to move away from their traditional migratory routes and important habitats.
Oil and gas exploration is expanding as our demand for energy increases. During these surveys, the ocean floor is blasted by high powered air guns. The echoes created off the ocean floor and the earth’s crust beneath it are recorded to map oil and gas reserves. The sound created by these blasts is on a similar level to that created by a fighter jet and can travel up to 4,000 kilometres underwater.
Other sources of noise are military sonar, echosounders (devices used to determine the depth of water), offshore constructions, marine windfarms, dredging activities, and many others. Not only do all of these noisy activities pose a high risk for whales and dolphins by drowning out their own communication and disrupting their lives, but noise can cause them injuries, including stress, organ and hearing damage. It can even kill.
Ocean noise is globally recognised as a major threat to marine ecosystems and scientists and conservationists are working together to try to better understand its impact. Organisations like Whale and Dolphin Conservation are raising the profile of the issue and calling on governments to protect the ocean and the incredible creatures that inhabit it. The good news about noise is that once you shut down the source, it disappears.
For more information visit whales.org/noise
Photo of humpback whale on the top of the page by V Mignon
Noise pollution is one of many issues in the oceans caused by human that will affect marine life, and in the ends ourselves. Are you also concerned? We have been working on a project that we call Stories for the Seas, which is a way for us to give back to the oceans that are giving us so much joy. Stories for the Seas is a coffee table book that will be launched for pre-orders next week. More about this here.